The present invention relates to robotics, and more specifically to an apparatus and method for automated archiving and retrieval of cartridges, such as those used in computer systems, to and from a mass storage system. However, the present invention may also be used in the archiving and retrieval of audio cassettes and the like.
In computer system environments, it is known to use robotic systems to archive and retrieve computer data storage media such as computer tape cassettes. Specifically, these systems use a type of robotic arm and hand to archive to or retrieve a cassette from a specific location in a storage library. The system then provides the cassette to a cassette drive unit. Certain systems use a system having a track disposed between drive unit and storage library, and a carriage assembly for moving along the track.
Certain systems place a platform upon the carriage assembly on which the robotic arm and hand are located. The robotic arm moves to a desired location in a storage library and using the hand, which may have a plurality of fingers, grips and removes a cassette from the location. The robotic system may then move to the drive unit and release its fingers, thereby placing the cassette within the drive unit. When desired, the robotic arm may then remove the cassette from the drive unit and replace the cassette within the storage library.
It is desired that selection, removal, and placement of a cartridge in a drive unit be accomplished as fast as possible, as computer systems have been incrementally increasing in their processing speeds. Because of these speeds, it is desired to archive and retrieve cartridges for placement within a drive unit as quickly as possible, so that the drive unit does not incur significant down time, during which it could otherwise be reading data from cartridges.
In aid of speeding this process, robotic systems such as those generally discussed above may be combined with a bar code scanner or other optical scanner to provide known locations of cartridges within a storage library, so that a desired cartridge may be chosen from a plurality of cartridges stored within the library. However, there are certain problems with the robotics and scanning of these known systems. First, the robotic arm often does not properly place or replace the cartridge within the library, thereby causing the cartridge to "bounce back" and not be secured within the library. Second, the requirement of optically scanning cartridges within the library is time consuming. Other problems relating to bar code scanning include the following: if a cartridge is not coded, or the code is nonreadable (i.e. defective or damaged label or unreadable label format), the scanner cannot identify the cartridge, and a system failure may result. Additionally, if a cartridge is not labeled or the label is not identifiable to the system, the system may try to place another cartridge in the same slot, thereby causing damage to the system and failure. Therefore, purely optical (scanner) methods are not ideal for cartridge identification and location information.